MCP vs A2A
Product engineer: Expose your product with MCP first; add A2A only if you ship an agent others delegate to. Developer-platform lead: Both now sit in the Agentic AI Foundation. Agent builder: Use MCP for tools and A2A for handing work to another agent.
The sourced difference
MCP connects an agent to tools, resources and prompts on a server; A2A connects agents to other agents through an Agent Card at /.well-known/agent-card.json and task messages over JSON-RPC, gRPC or HTTP+JSON. (MCP: Model Context Protocol specification (latest, 2026-07-28), read 5 November 2026; A2A: A2A specification, read 5 November 2026)
Verdicts by reader
| Reader | Verdict |
|---|---|
| Product engineer | Expose your product with MCP first; add A2A only if you ship an agent others delegate to. |
| Developer-platform lead | Both now sit in the Agentic AI Foundation. |
| Agent builder | Use MCP for tools and A2A for handing work to another agent. |
Side by side
| Aspect | MCP | A2A |
|---|---|---|
| Maintainer | MCP maintainers under the Agentic AI Foundation | A2A project, Growth Stage project at the Agentic AI Foundation (Linux Foundation-directed) |
| What it is | A JSON-RPC 2.0 protocol between hosts, clients and servers; servers offer tools, resources and prompts, and clients may offer elicitation. | A protocol for agents to discover each other through an Agent Card and exchange tasks and messages. |
| Status and version | Current revision 2026-07-28 (released 28 Jul 2026); prior revision 2025-11-25. Registry in preview with API v0.1 frozen since 24 Oct 2025. | Specification 1.0.0 is the latest release; joined the Agentic AI Foundation on 27 Aug 2026. |
| What it does not do | Does not grade servers, verify registry entries, or prescribe a .well-known discovery file in the 2026-07-28 core spec; server cards are still Working Group work. | Does not define how an agent calls a plain API or a web page; it covers agent-to-agent tasks, not tool access. |
Read the full entries: MCP and A2A.
Seen in the shared crawl
| Path | Top 10,000 found | Ora leaderboard found |
|---|---|---|
/.well-known/mcp.json | 19 of 7,470 (0.25%) | 66 of 3,366 (1.96%) |
A path counts only when the answer is the right kind of document. Many sites answer these paths with an ordinary web page, which is not counted. See the census.
| Path | Top 10,000 found | Ora leaderboard found |
|---|---|---|
/.well-known/agent-card.json | 10 of 7,470 (0.13%) | 48 of 3,368 (1.43%) |
/.well-known/agent.json | 6 of 7,461 (0.08%) | 14 of 3,366 (0.42%) |